Pentapotassium dodecatungstoborate(III) hexadecahydrate

The title compound, K(5)[BW(12)O(40)].16H(2)O, contains a [BW(12)O(40)](5-) polyanion of 222 crystallographic symmetry, with a central tetrahedrally coordinated B(III) atom surrounded by four groups of three edge-sharing octahedra (W(3)O(13) subunits), which are linked in turn to each other and to the central BO(4) tetrahedron by shared O atoms at the vertices. There is a crystallographically unique B-O bond of 1.554 (10) A, while the average W-O distances are 2.344 (17) A for four coordinate O atoms, 1.917 (12) and 1.89 (2) A for two coordinate O atoms within and connecting the W(3)O(13) subunits, respectively, and 1.709 (8) A for terminal O atoms. Not all of the K(+) ions and H(2)O groups were located.